Anther wall and pollen development in Aspidosperma Mart & Zucc. (Apocynaceae).

This article focuses on the embryological development of anther walls and pollen grains in five species of Aspidosperma, a genus within the Aspidospermateae tribe of the Apocynaceae family. Using light and electron microscopy, the study found that Aspidosperma species exhibit a dicotyledonous anther wall development characterized by a fibrous endothecium, a one-layered middle layer, and a secretory tapetum with uninucleate cells, alongside simultaneous cytokinesis during microsporogenesis. Pollen grains were observed to be 4–6 colporate or pseudocolporate, with distinctive ridges formed by uneven infratectum layer deposition, which may relate to harmomegathy—the pollen's ability to accommodate dehydration and rehydration during pollination. These pollen wall features appear consistent across the tribe Aspidospermateae and may represent a synapomorphy, although further studies on other genera are recommended to confirm evolutionary trends within Apocynaceae.